Honeywell HIH-6130 Series Manuals

Technical Note Using Alarms on the Honeywell HumidIcon™ Digital Humidity/Temperature Sensors: HIH-6130/6131 Series Sensing and Control 1.0 Introduction The Honeywell HumidIcon™ Digital Humidity/Temperature Sensors: HIH-6130/6131 Series support up to two configurable alarm outputs which can be used to monitor whether the ambient humidity has risen or fallen below preprogrammed values. The alarms have configurable thresholds, polarity and outputs to provide flexible interfacing with other components. This document describes: Alarm functionality How to combine alarms Configuration options How do disable alarms 2.0 Alarm Output The alarm output can be used to indicate whether a predefined humidity level has been reached. The alarms can be configured in two ways: As an open-drain output to drive a load connected to VDD (see Figure 1). Figure 1. Alarm Open Drain Output Application Circuit Example Digital Humidity/ Temp. Sensor VDD VCORE VSS NC SCL SDA ALARM_LOW ALARM_HIGH VSUPPLY = 2.3 Vdc to 5.5 Vdc GND 0.1 µF 0.22 µF 8 3 4 5 6 1 2 7 As a full push-pull driver for interfacing with a microcontroller or to drive a high voltage external device, (see Figure 2). Figure 2. Alarm Push-Pull Output Application Circuit Example GND Digital Humidity/ Temp. Sensor VDD VCORE VSS NC SCL SDA ALARM_LOW ALARM_HIGH VSUPPLY = 2.3 Vdc to 5.5 Vdc GND 0.1 µF 0.22 µF 8 3 4 5 6 1 2 7 GND 12 V 12 V If available, both alarms can be used at the same time. The alarm outputs are updated when a measurement cycle is completed. 3.0. Alarm Functionality There are four registers associated with the alarm thresholds (see Appendix A for the EEPROM addresses): Alarm_High_On Alarm_High_Off Alarm_Low_On Alarm_Low_Off Each register contains a 14-bit value that determines the humidity at which the alarm turns on or off. The two Alarm_High registers set the hysteresis of the Alarm_High pin, while the two Alarm_Low registers set the hysteresis for the Alarm_Low pin (see Figure 3). Figure 3. Alarm Hysteresis Alarm_High_Off Alarm_High_On Alarm_Low_On Alarm_Low_Off Humidity Time High Alarm On High Alarm Off Low Alarm On Low Alarm Off NOTICE Alarm registers may only be accessed using Command Mode. (See Technical Note “Entering and Using Command Mode on Honeywell Digital/Temperature Sensors”.) Alarm_High_On register determines the humidity threshold where the high alarm is activated. Alarm_High_Off register determines the humidity threshold where the high alarm is deactivated. Alarm_Low_On register determines the humidity threshold where the low alarm is activated. Alarm_Low_Off register determines the humidity threshold where the low alarm is deactivated. Using Alarms on the Honeywell HumidIcon™ Digital Humidity/Temperature Sensors: HIH-6130/6131 Series 2 Honeywell Sensing and Control The contents of the alarm registers correspond to humidity as follows: Humidity (%RH) = RegisterContents (214 - 1) x 100% Thus, 0 %RH = 0x0000 and 100 %RH = 0x3FFF or 16383. For example, to enable the Alarm_High output at humidity above 80 %RH: Alarm_High_On = 80 %RH 100% x (214 - 1) = 13107 or 0 x 3333 Similarly, to enable the Alarm_Low output at humidity below 10 %RH: Alarm_Low_On = 10 %RH 100% x (214 - 1) = 1638 or 0 x 0666 Alarm hysteresis is equivalent to the difference between the registers. A minimum hysteresis of 3% RH is recommended. High and Low Alarm flow charts are shown in Figure 4. Figure 4. High and Low Alarm Flow Charts High Alarm Alarm = Off Measurement > Alarm_High_On? Alarm = On Measurement < Alarm_High_Off? Yes Yes No No Low Alarm Alarm = Off Measurement < Alarm_Low_On? Alarm = On Measurement > Alarm_Low_Off? Yes Yes No No 4.0 Alarm Configuration A fifth register, the Customer Configuration Register (see Appendix B), is associated with the alarm outputs and contains the configuration bits. Both alarms may be configured independently using the Alarm_Low_Cfg and Alarm_High_Cfg bits (see Table 1). Table 1. Customer Configuration Register Alarm Bits Bit Description 7 Alarm_Low Polarity: 0 = Active_ High, 1 = Active_ Low 8 Alarm_Low Output Configuration: 0 = Full_Push-Pull, 1 = Open_Drain 9 Alarm_High Polarity: 0 = Active_High, 1 = Active_Low 10 Alarm_High Output Configuration: 0 = Full_Push-Pull, 1 = Open_Drain For applications which interface to other logic circuits, such as a micro-processor or to drive an external device, Full Push-Pull is recommended. For driving loads directly connected to the sensor voltage supply open drain would be a typical choice (see Figures 1 and 2). The polarity of the alarm output is configured using the Alarm Polarity bits. The ability to change the alarm polarity gives the user flexibility in how the sensor interfaces with an application. In the example shown in Figure 1, the alarm outputs are used to control an LED. For the LED to light up when the alarm is on or active, the alarm output must be low, so the alarm polarity bit should be set to 1, Active_Low. 5.0 Creating Two High or Two Low Alarms The Alarm Polarity bits also give the user the option to create two high alarms or two low alarms. Consider an application requiring two high alarms. Conventionally, if the Alarm_Low Polarity is configured as Active High, then the Alarm_Low output will become active (goes high) when the humidity falls lower than the humidity value represented in the Alarm_Low_On register and becomes inactive (goes low) when the humidity rises above the humidity value represented in the Alarm_Low_Off register. Similarly, if the Alarm_High Polarity is configured as Active High, then the Alarm_High output will become active (goes high) when the humidity rises above the humidity value represented in the Alarm_High_On register and becomes inactive (goes low) when the humidity falls below above the humidity value represented in the Alarm_High_Off register (see Figure 5). Using Alarms on the Honeywell HumidIcon™ Digital Humidity/Temperature Sensors: HIH-6130/6131 Series Honeywell Sensing and Control 3 Figure 5. Alarm Outputs with Active High Polarity Alarm_High_Off Alarm_High_On Alarm_Low_On Alarm_Low_Off Humidity Time Alarm_High Output = 1 Alarm_High Output = 0 Alarm_Low Output = 1 Alarm_Low Output = 0 Alarm_Low Output = 0 Alarm_High Output = 0 If the polarity of the Alarm_Low output is changed to Active Low then the Alarm_Low output will be high when the humidity is above the humidity value stored in the Alarm_Low_Off register and low when the humidity is less than humidity value in the Alarm_Low_On register (see Figure 6). Figure 6. Alarm Outputs with Active Low Polarity Alarm_High_Off Alarm_High_On Alarm_Low_On Alarm_Low_Off Humidity Time Alarm_High Output = 1 Alarm_High Output = 0 Alarm_Low Output = 0 Alarm_Low Output = 1 Alarm_Low Output = 1 Alarm_High Output = 0 By reversing the polarity of Alarm_Low, its output now behaves in the same manner as Alarm_High, in other words, as a second high alarm; however, the effect of the alarm registers also reverses. The Alarm_Low_On register acts like the Alarm_High_Off register, while the Alarm_Low_Off register acts like the Alarm_High_On register. The same steps can be done to create two low alarms. Reverse the polarity of Alarm_High and the functions of the Alarm_High_On and Alarm_High_Off registers will also switch. 6.0 Disabling Alarms If an application does not require the use of alarms, then the alarms may be disabled by setting registers Alarm_High_On and Alarm_High_Off to their maximum value (0x3FFF) and registers Alarm_Low_On and Alarm_Low_Off to their minimum value (0x0000). In this configuration the alarm outputs must be left unconnected in the application. 7.0 Appendices 7.1 Appendix A. EEPROM Memory Map Table 2 shows the EEPROM Memory Map. Table 2. EEPROM Memory Map EEPROM Address Default Name Description 0x00 to 0x15 N/A reserved do not change; must be left at factory settings; locked EEPROM locations 0x16 0x0000 reserved do not change; must be left at factory settings 0x17 0x0000 reserved do not change; must be left at factory settings 0x18 0x3FFF Alarm_High_On high alarm on trip point 0x19 0x3FFF Alarm_High_Off high alarm off trip point 0x1A 0x0000 Alarm_Low_On low alarm on trip point 0x1B 0x0000 Alarm_Low_Off low alarm off trip point 0x1C 0x0027 Cust_Config Customer Configuration Register (see Section 4.0) 0x1D 0x0000 reserved do not change; must be left at factory settings 0x1E 0xYYYY (Y=data) Cust_ID2 customer ID word; for use by customer 0x1F 0xYYYY (Y=data) Cust_ID3 customer ID word; for use by customer 7.2 Appendix B. Customer Configuration Register The Customer Configuration Register (see Table 3) is located at EEPROM address 0x1C. It can only be accessed using Command Mode.